1. Field of the Invention
The present invention relates to a method and device for adjusting and setting the alignment of a radar for automobiles, especially the alignment of the radio axis of the radar with respect to a determined direction relative to the vehicle. The method and the device can be applied especially to the alignment of the radio axis of the radar on the axis of thrust of the vehicle.
Several types of radars can be fitted into automobile vehicles. These include ACC or  less than  less than Automotive Cruise Control greater than  greater than  type radars. One radar of this type is used to regulate the pace of the vehicles. It detects and locates the closest vehicle that is in the path of the carrier. For this application, the radar requires, for example, a range of about 150 meters. In particular, it must be able to ascertain that a vehicle is located in the path of the carrier at this distance. Because there are sources of inaccuracy that play a role in the angular localization, the radio axis of the radar must be aligned azimuthally with the tangent to the trajectory of the carrier vehicle. The axis of thrust is the tangent to the trajectory followed by the vehicle when the conductor releases the steering wheel. For a vehicle that has no serious defects, especially as regards the geometry of the wheel assemblies or the quality of the tires, this path is a straight line or a curve with a wide radius of curvature. The axis of thrust is very substantially the bisectrix of the angle formed by the horizontal projection of the axes of the rear wheels. The radio axis is the axis along which the radar measures an angular variation of zero for an object located on this axis. The alignment must be measured to a precision of more than 0.20xc2x0 approximately. This constitutes a very precise alignment. The operation of adjusting and setting this alignment consists in making the radio axis of the radar parallel to the axis of thrust of the carrier vehicle.
For reasons that take account of the aesthetic aspects of the vehicle, the radar is positioned behind a body element or it is concealed behind a cover. The body element or the cover is made of a material especially designed so that microwaves undergo little or no attenuation and deflection.
It should be possible to align the radar quickly and precisely on the assembly line. Just like the alignment of the headlights and the setting of the parallelism of the wheels, the alignment of the radar is part of the final operations for the manufacture of the vehicle. It should be possible to do the alignment simply and automatically. In particular, this operation should not call for any operation of disassembly.
2. Description of the Prior Art
To adjust and set the alignment, several adjusting and setting techniques are known. Certain techniques implement an optical or electro-optical device.
Such techniques require optical access to the radar, either to fit in a set of tools or to provide for a precise lateral localization of the radar with respect to the assembly used for the alignment. These constraints require that the alignment should be adjusted before the installation of the xe2x80x9caesthetic coverxe2x80x9d. This means that only an a priori correction can take account of an axial deviation, if any, caused by the aesthetic cover of the radar. Thus, this technique is not enough, by itself, for an adjusting and setting operation that fulfils the requirements of alignment. It requires an assessment of the axial deflection that may be introduced by the aesthetic cover. In addition, the aesthetic cover cannot be mounted until after the adjustment and setting of the alignment. If not, an operation to dismantle said cover must be done before the adjustment and setting operation. This constraint is not very compatible with vehicle assembly lines.
The invention is aimed especially at overcoming the above drawbacks. To this end, an object of the invention is a method for adjusting and setting the alignment of the radio axis of a radar installed on a vehicle parked on a running surface, with respect to a determined direction relative to the vehicle, by means of a adjustment and setting stand comprising a goniometer-responder assembled on an axis of motion perpendicular to the axis of the stand, wherein the method consists in:
acquiring the angles xcex1 and xcex2, xcex1 being the azimuthal angle at which the radar perceives the goniometer-responder and xcex2 being the angle between the determined direction and the axis of the stand,
determining the azimuth xcex3 of the radar by means of the goniometer-responder when the radar, configured in test mode, sends out a continuous frequency,
equalizing the azimuth xcex3 with the angle xcex2 by translating the goniometer-responder along its axis of motion,
nullifying the angle of azimuth xcex1 by actuating the means to adjust the radar in azimuth.
An object of the invention is also an adjustment and setting stand to implement the method, comprising:
a reference axis related to the running surface,
a goniometer-responder, positioned with respect to the running surface and having a frequency band compatible with that of the radar, for the angular localization, by angular deflection, of the radar when the radar sends out a continuous frequency in a test mode,
an interface and control device connected to the radar to configure the radar in test mode and acquire the azimuth a of the goniometer-responder measured by the radar.
The method especially enables the precise alignment of the radio axis of the radar with the axis of thrust of the carrier vehicle. The method does not require any disassembly. It can be automated. It can just as easily be implemented in an assembly line, after the final stage of assembly, and in a garage during maintenance work.
The device comprises a goniometer-responder for which the majority of the specifications can be deduced from the specifications of the radar. This characteristic makes it possible to manufacture the device according to the invention at very low cost. The device is compact. It can be integrated into a vehicle assembly line.